2026/04/29 by Pralay Biswas, Ramananda Santra, Ruta Kale +1 · 1 voice
Physics and Astronomy · #astro-ph.GA
paper · pdf · doi:10.3847/1538-4357/ae64e6
arxiv published 2026/04/29 · arxiv updated 2026/06/01
Giant radio halos are the Mpc-scale extended sources associated with the merging clusters, while the mini-halos are preferentially associated with cool-core clusters. Both trace the ICM plasma physical process, and recent low-frequency observations increasingly blur the distinction between the two classes. We present the first multi-frequency spectral analysis of the galaxy cluster RXCJ0232--4420, hosting a cool core, using uGMRT (400 and 650 MHz) and MeerKAT (1283 MHz) observations. The central radio emission extends beyond ∼ 1 Mpc at all frequencies, confirming it as a giant radio halo. One candidate relic (in the east) has also been detected, with an extent of ∼ 300 kpc. The integrated spectral indices of halo and candidate east relic are α= -1.17 ± 0.17, and α= -0.85 ± 0.17, respectively. The resolved spectral map of the halo is mostly uniform (-1.0 to -1.3) and does not show any radial steepening. The radio surface brightness profile is well modelled by a single exponential law, with the e-folding radius constant across frequencies. The radio halo emission is morphologically well correlated with the thermal emission. Point-to-point radio-X-ray correlation analysis gives a sublinear relationship (slope ∼ 0.80), with no frequency evolution. The presence of Mpc-scale emission in the cool-core cluster shows that such emission can arise in dynamically intermediate systems. Our results demonstrate that merger-driven turbulence, even from minor disturbances, can sustain cluster-wide particle re-acceleration without destroying the cool core.